The invention relates to an optoelectronic device for detecting objects in a monitoring range with a distance sensor, the device including a transmitter for transmitting light rays; a deflection unit on which the transmitted light rays are reflected for periodically sweeping the transmitted rays over the monitoring range; a receiver for receiving light rays; and an evaluation unit for evaluating the signals received at the receiver.
A device of this type is disclosed in German Patent 39 32 844 C2. The device has a distance sensor that operates according to the triangulation principle and comprises a transmitter for transmitting light rays as well as a receiver which receives light rays and is connected to an evaluation unit. The transmitted light rays are deflected by a deflection unit with a deflection mirror, so that these rays periodically sweep over a monitoring range. The position of the objects is detected by determining the actual angular position of the deflection unit and the range values determined with the aid of the distance sensor.
The dimensions of the monitoring range are stored in the evaluation unit in the shape or outline contour of the monitoring range, in sequential pairs of range and angle values.
In order to detect an object, its position is detected by recording the associated range and angle values. These range and angle values are compared to the stored outline contour of the monitoring range. If it turns out that the object is located inside of the monitoring range, then a signal transmission is triggered.
A disadvantage of this method is that only one monitoring range is stored in the evaluation unit. In practical applications, however, objects frequently must be detected with the aid of an optoelectronic device in different monitoring ranges having different dimensions. For example, if an optoelectronic device is mounted on the front of an unmanned transport vehicle for monitoring the area in front of the vehicle, the dimensions of the monitoring range can depend on whether the vehicle moves in a corridor along a predetermined track or whether it moves freely inside a hall.
For applications of this type, the optoelectronic device is used in particular in the area of protection of persons, so that the optoelectronic device must meet technological safety standards. It is essential that the selection of suitable monitoring ranges also ensures a correspondingly high protection against errors.
German Patent 197 21 105 A1 relates to an optoelectronic sensor, comprising a light transmitter for transmitting a light beam into a monitoring range, as well as a receiver for receiving a light beam formed by the transmitted light that is reflected by an object in the monitoring range. In this case, the angle of the received light beam changes relative to the transmitted light beam, in dependence on the distance between the object and the sensor. The sensor also comprises a control and evaluation unit for processing the output signal from the light receiver. The light receiver is provided with a multi-element light sensor, comprising at least four individual sensor elements, which are arranged next to each other, such that the light beam is admitted to different sensor elements depending on the beam angle. The signal outputs for the sensor elements are connected to switches, wherein the sensor can be adjusted to different reference distances for an object by actuating the switch.